Nineteen young professionals including Tian Tingting (above) and Li Yidong restore ancient books at the National Library of China in Beijing. JIANG DONG/CHINA DAILY

Li Yidong starts his day much like a baker. He makes a ball of dough, kneads it, allows it to rise and then washes the dough with water to extract the crucial ingredient: starch.

The 28-year-old is one of 19 book restorers at the National Library of China in Beijing, which is home to the world's largest collection of ancient Chinese books.

One of the first skills they learn is how to make a starch paste to glue together old pages.

"We don't use starch from the market," says Li. "Our teacher says there can be food additives in it. Proper strength is needed in restoration, so handmade paste is vital."

This year marks the 10th anniversary of the founding of the National Center for Preservation and Conservation of Ancient Books, which is headquartered in the library.

In China, "ancient books" refer to those published before the fall of the Chinese monarchy in 1911. In this library, there are 2.7 million such books.

The center estimates that there are about 50 million ancient books housed in the country's public institutions, but China had less than 100 full-time restorers for them before 2007, according to Chen Hongyan, director of ancient book department of the NLC.